Optical properties of ZnO nanorods and hybrid structures grown on p-type GaN/sapphire and silicon-on-insulator substrates

In this study, we report on the optical properties of ZnO nanorods and hybrid structures grown on p-GaN and silicon-on-insulator (SOI) substrates. Strong band-edge emission with negligible deep level emission in room-temperature photoluminescence (PL) spectra suggested good crystalline quality nanorods and hybrid structures on both substrates. The presence of E^high₂ optical phonon modes centred around 438.5 cm^-1 in the visible Raman spectra demonstrates the wurtzite nature of ZnO hybrid products on both substrates. The red shifts of the near-band-edge room-temperature PL spectra from the hybrid structures reveal the presence of in-plane stress in the top ZnO layers overgrown on nanorod arrays. Furthermore, the hybrid structures exhibit stronger contribution of disorder activated phonon mode at 460 cm^-1 in the ultraviolet Raman spectra. The softening of first-order LO phonon mode in the UV Raman spectra of hybrid structure on SOI is associated with the presence of surface defects. Such hybrid ZnO structures may be suitable for integrated nanophotonics.